In a developing device of an image forming apparatus of electrophotographic system, such as a copying machine or a printer, there is an apparatus in which toner is supplied to the developing device by an attachable and detachable toner cartridge. Besides, there is an apparatus including a falling toner receiver to receive the toner spilled when a toner cartridge is attached to and detached from the image forming apparatus.
However, if the falling toner receiver is uncovered, there is a fear that during the attachment and detachment operation of the toner cartridge, an operator touches the toner collected in the falling toner receiver, and a large amount of toner adheres to the operator and contaminates the surroundings.